Deborah Johnston, from Glasgow, was six months pregnant with identical twins Theo and Olly when she was diagnosed with life threatening twin to twin transfusion syndrome (TTTS).
The twins survived thanks to urgent laser surgery and constant monitoring and care from doctors and staff at Wishaw General Hospital and the Queen Elizabeth University Hospital in Glasgow.
Deborah, 42, spoke out to thank the medics who acted at the height of the pandemic and to mark World TTTS Awareness Day on Tuesday.
The mum, who has also received support from the national charity Twins Trust, said: "My partner Scott and I were over the moon when we were told we were having twins -- we'd always wanted twins.
"We will be forever grateful for the care we received and to everyone who helped us on our journey.
"Theo and Olly are the happiest babies I've ever seen. I hope they can give hope to other families."
TTTS is a rare condition that affects only identical twins who share one placenta, and occurs randomly when there is an imbalance in the blood exchange between the twins.
One twin, the donor, loses more blood than he or she receives and risks malnourishment and organ failure while the recipient twin receives too much blood and can suffer cardiac and other complications.
Deborah, who also has a four-year-old daughter, Rosie, had never heard of TTTS until she became pregnant with identical twins and was told she was at a high risk. But at just over 26 weeks pregnant she faced an agonising choice to save her babies' lives before they were even born.
If she did nothing, she would likely lose both twins, while draining fluid might only have helped one sibling. Meanwhile, undergoing surgery, known as endoscopic laser ablation, would give both babies a roughly one in three chance of survival. As she was over 26 weeks pregnant, surgery would be complicated by the thickness of the blood vessels.
Deborah felt surgery was the only option, but feared history repeating itself. Remarkably, both her parents had lost a twin sibling at birth.
She said: "We were told about the condition at the first appointment with the consultant, but you hope and pray it won’t happen to you.
"Then, at one of my scans, it became clear there was lots of fluid surrounding one twin and not as much around the other."
Deborah was being scanned twice a week, but woke one morning in such discomfort she could barely move.
A scan at Wishaw General Hospital indicated an abnormal reduction in amniotic fluid around one twin caused by a loss of blood volume to his brother.
She was immediately referred to the Queen Elizabeth Hospital where a specialist informed her that both twins were very poorly and offered her three options.
Deborah said: "I was devastated but laser surgery seemed the only option as it gave us hope. I was shocked that there was only a 33% chance both our boys would make it because they were so poorly, but we clung onto that hope.
"Both my mum and my dad were twins and both of them lost their twin at birth, and it was in the back of my mind that it could happen again. The next day we heard two heartbeats and the relief was incredible."
The following days were critical but the condition did not return. Deborah gave birth to twins Theo (4lb 6) and Olly (4lb 7) via a planned c-section on 24 November 2020.
The brothers spent four days in neonatal care and then special care for a further ten days before being allowed home in time for Christmas. They recently celebrated their first birthdays.
Deborah said: "They were tiny, but they were perfect. Taking them home in time for Christmas was the best present ever. I'm so grateful for the care we received, especially during the pandemic."
Helen Peck, Scottish coordinator for Twins Trust, the only UK-wide charity dedicated to improving the lives and wellbeing of families with twins, triplets or more, said: "World TTTS Day helps raise awareness of this serious, but often treatable condition.
"Everyone expecting twins or multiples should know the signs of TTTS and feel empowered to talk to their health care provider if they have concerns."Twins Trust has resources to help parents understand the condition, spot the symptoms and advocate for the care they need.”